Regulation of cytoskeletal mechanics and cell growth by myosin light chain phosphorylation

• Published in: American Journal of Physiology: Cell Physiology Vol. 275; no. 5; pp. C1349 - C1356
• Main Authors: Cai, Shuang, Pestic-Dragovich, Lidija, O'Donnell, Martha E, Wang, Ning, Ingber, Donald, Elson, Elliot, De Lanerolle, Primal
• Format: Journal Article
• Language: English
• Published: United States 01.11.1998
• Subjects: 3T3 Cells; Animals; Calcium-Calmodulin-Dependent Protein Kinases - metabolism; Cell Adhesion - physiology; Cell Division; Cytoskeleton - physiology; Cytoskeleton - ultrastructure; Homeostasis; Kinetics; Mice; Myosin Light Chains - metabolism; Myosin-Light-Chain Kinase - metabolism; Phosphorylation; Recombinant Proteins - metabolism; Stress, Mechanical; Transfection; Non-programmatic
• ISSN: 0363-6143; 0002-9513; 1522-1563; 2163-5773
• DOI: 10.1152/ajpcell.1998.275.5.c1349

1  Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, Illinois 60612-7342; 2  Department of Human Physiology, University of California, Davis, California 95616-8644; 3  Physiology Program, Harvard University School of Public Health, Boston, 02115-6021; 4  Departments of Pathology and Surgery, Children's Hospital and Harvard University Medical School, Boston, Massachusetts 02116-5737; and 5  Department of Biophysics and Molecular Biophysics, Washington University Medical School, St. Louis, Missouri 63110-1093 The role of myosin light chain phosphorylation in regulating the mechanical properties of the cytoskeleton was studied in NIH/3T3 fibroblasts expressing a truncated, constitutively active form of smooth muscle myosin light chain kinase (tMK). Cytoskeletal stiffness determined by quantifying the force required to indent the apical surface of adherent cells showed that stiffness was increased twofold in tMK cells compared with control cells expressing the empty plasmid (Neo cells). Cytoskeletal stiffness quantified using magnetic twisting cytometry showed an ~1.5-fold increase in stiffness in tMK cells compared with Neo cells. Electronic volume measurements on cells in suspension revealed that tMK cells had a smaller volume and are more resistant to osmotic swelling than Neo cells. tMK cells also have smaller nuclei, and activation of mitogen-activated protein kinase (MAP kinase) and translocation of MAP kinase to the nucleus are slower in tMK cells than in control cells. In tMK cells, there is also less bromodeoxyuridine incorporation, and the doubling time is increased. These data demonstrate that increased myosin light chain phosphorylation correlates with increased cytoskeletal stiffness and suggest that changing the mechanical characteristics of the cytoskeleton alters the intracellular signaling pathways that regulate cell growth and division. cell stiffness; osmotic swelling; volume regulation; mitogen-activated protein kinase activation; cell division; myosin light chain kinase